The invention relates to a method for dual curing a RMA crosslinkable resin coating, to RMA crosslinkable compositions and to resins for use in the method. The RMA coating method and composition can be used for direct to concrete application, to wood coatings and coatings that are easy-to-clean, anti-graffiti and sanitisable coatings
A variety of different types of resins are known in the prior art that can form the binder of a coating composition. The dominant technologies that are currently being used are epoxy-amine and polyol-polyisocyanate. Although these resin systems have their merits, they also pose some important limitations as the use chemicals that have toxicological profiles that are questionable (bisphenol A/F in epoxy resins, amine curing agents, monomeric diisocyanate in polyisocyanate hardeners). A further disadvantage of polyol-polyisocyanate floor coating systems is that, during the application, they are moisture sensitive. Epoxy-amine floor coating systems have a further disadvantage that they cannot be cured at relatively low temperatures below 15 or 10° C. which may often occur in outdoor applications. Consequently, there is a desire for a coating composition that has a more favorable toxicological profile, can be cured also at low temperatures and also in moist conditions.
Another important parameter for coating applications is the working time. This is the time following mixing of the basic ingredients during which the coating can be applied and finished without detrimental effect on its properties such as adhesion, compaction and surface finish. This property is very much linked to the consistency of the resin. Epoxy-amine and polyol-polyisocyanate systems will start reacting chemically already in the liquid state directly after mixing. This implies that the viscosity of the mixed liquid resin flooring will start to increase, reducing the fluidity and the ability of the resin flooring to flow and level. Coating compositions having a good working time are known. For example alkyd resins have a good working time. However but take a rather long time to cure and fully develop the mechanical properties required for the end use (service time). This limits the use to relatively thin layers which harden faster than thick layers and also leaves a desire for better mechanical properties and chemical resistance of the resulting cured coating. Therefore there is still a desire for coating compositions with a more favorable balance of the counteractive requirements of working time and time to service.
Another desire is that the coating compositions have a low volatile organic content for safety, environmental and health reasons, in particular when applied in poorly ventilated circumstances, in particular indoor. This requirement is contra-active to achieving a higher fluidity and improved working time through the use of a volatile organic solvent. With volatile solvent herein is meant, unless otherwise described, the organic compounds having a boiling point below 250° C. present in the composition ready for use.
Apart from the above requirements the coating preferably also has a very good adhesion to the substrate and has a good water and chemical resistance, a high resistance to impact and abrasion, an optically attractive surface, a low dirt pickup- and adhesion and be easy to clean.